1. Field of the Invention
This invention relates to optical multivibrators and, in particular, to optical square-wave multivibrators. Accordingly, it is a general object of this invention to provide new and improved multivibrators of such character.
2. General Background
Optical square waves such as digital optical signals are suitable for modulation to carry information in optical signal processing systems. Optical square waves, such as optical clock pulses, can be used as timing signals.
One prior art method of generating optical square waves involves driving a semiconductor laser ON and OFF with electrical square-wave current. This method, however, suffers from slow response because its speed is limited by the associated electrical square-wave generator and by the carrier lifetime of the semiconductor laser. Furthermore, a separate electrical circuit for the generation of the electrical square-wave current was required.
Another prior art method of generating optical square waves involves chopping a light beam by mechanical, electrical, or electro-optic means. However, this method, basically, involves modulating a light beam instead of an active square-wave light source. Although electro-optic modulation can be very fast, other types of modulation are slow in response.